Typically semiconductor chips are attached to organic circuitized substrates by means of a polymeric, organic, adhesive. The adhesive, which initially is in the form of a viscous liquid, is distributed onto preselected regions on the circuitized surface. Thereafter, the perimeter of the semiconductor chip is aligned with and placed on the adhesive. The entire structure, including substrate, adhesive and chip, is then baked to cure the adhesive to thereby strengthen the attachment of the semiconductor chip to the underlying substrate. In some cases, the semiconductor chip is then electrically connected to the electric circuitry of the carrier by wire bonding terminals on the chip to wire bond sites that form part of the circuitry on the surface of the substrate.
The adhesives that are currently used to attach semiconductor chips to circuitized organic substrates include for example, epoxy-based adhesives, acrylic-based adhesives, silicones, and polyimides. Although such adhesives are fairly viscous, they still have a tendency to spread over the surface of the underlying substrate, which is formed from an organic resinous material. Such adhesives also have a tendency to spread over any portions of a soldermask which lie in the vicinity of the deposited adhesive. The expanding adhesive may also come into contact with and cover portions of the wire bond sites that are on the surface, thereby interfering with attachment of the bonding wires to the wire bond sites. The problem of adhesive spread is even more pronounced when the circuitized substrate is treated with a plasma containing oxygen, argon or mixtures thereof prior to application of the adhesive to the circuitized substrate. Such plasma treatment is often used to clean the wire bond sites and to roughen the substrate surface.
Accordingly, a method of controlling the spread of an adhesive over the surface of a circuitized organic substrate would be highly desirable. A method which reduces the spread of the adhesive on the surface of the organic substrate and which does not interfere with the bonding of the bonding wires to the wire bond sites is especially desirable.